Investigating the factors influencing the bridging of dry non-crimp fabric on a concave L-shaped mould in an automated draping process

Figures & data

Figure 1 Bridging of dry NCF in L-shaped mould (left) and resin-rich zone in a FRP component (right)

Figure 2 First layer (left) and third layer (right) of used triaxial NCF for the draping process, stitching parameters are listed in table 1

Table 1 Properties of used triaxial NCF

Property/Parameter		Value	Unit	Material
Grammage	First layer (-45^∘)	300	g/m^2	E-Glas
	Second layer (45^∘)	300	g/m^2	E-Glas
	Third layer (0^∘)	240	g/m^2	E-Glas
	Stitching	14	g/m^2	Polyester
Stitching	Stitching pattern	Tricot-warp	–	–
	Stitch length	3	mm	–
	Gauge	5	1/cm	–
	Thread density:
	- First layer (-45^∘)	4	1/cm	–
	- Third layer (0^∘)	4	1/cm	–

Figure 3 Used sample geometry (left) and schematic representation of the edge curvature (right)

Figure 4 Draping of a dry NCF in a L-shaped mould (left), bridging after draping and value for the spring-back (right)

Figure 5 Used mould (left) and draping tool (right) for the automated draping process, all dimensions are given in millimetres (mm)

Figure 6 Automated draping process

Table 2 Factors influencing the bridging of dry NCF in an automated draping process (bold: variable factors, italic: varying factors and normal: constant factors)

Environment	Material	Mould	Process	Draping tool	Robot
Ambient temperature	Imper- fections	Geometry	Production of the sample(dim.)	Geometry	Positioning accuracy
Humidity	Mechanical properties - Bending stiffness - Viscoelastic behavior	Manufac- turing deviations	Manual lay-up - Orientation - Fixation	Manufac- turing deviations	Acceleration
		Deviations in orien- tation	Surface scanning error	Concept (e.g. roll or slide)	Velocity (v)
			Orientation of the sample - Top vs. bottom - Angle		Force (F)

Figure 7 Schematic illustration of different drape force states

Figure 8 Illustration of variables to calculate the spring-back during draping (left) and surface scanning (right) for a profile cross section (for the origin of the coordinate system see figure 5)

Figure 9 Average curves (n = 6) of spring-back against draping position for different velocities - exemplary curves for v = 10, 70 and 130 mm/s

Table 3 Investigated levels of the factors (input variables) for preliminary tests

Factors (input variables)	Levels
Velocity v in mm/s	10	50	100	150	200	250	350
Force F in N	2	5	10	15	20
Time between draping and surface scan tds in s	1, 2,…, 20	40	100	160	220	280

Table 4 Investigated levels of the factors velocity and force (input variables) for the main tests

Factors (input variables)	Levels
Velocity v in mm/s	5	10	30	50	70	90	110	130	150	200
Force F in N	2	4	6	8	10

Figure 10 Spring-back-curves for different velocities - exemplary curves for v = 10, 70 and 130 mm/s and its boxplots. The boxes and their whiskers indicate minimum, maximum, quartiles and median (basic boxplot withouts outliners) [24]

Figure 11 Boxplots of average curves of spring-back against velocity

Figure 12 Average curves (n = 6) of spring-back against draping position for different forces - exemplary curves for $F=2, 6$ and 10 N

Figure 13 Boxplots of average curves of spring-back against force

 Mittag HJ. Statistik: Eine Einführung mit interaktiven Elementen. 4th ed. Springer Berlin Heidelberg; 2015. Available from: doi: 10.1007/978-3-662-47132-6.

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